Heat pumps provide heating in winter and cooling in summer.

While they’re OK for moderate climates, they are not efficient in extreme cold climates. Building on work that began five years ago, researchers at Purdue University are developing a new type of heat pump that is much more efficient and could allow residents in cold climates to cut their heating bills in half.

The innovation aims to improve efficiency in general but is especially practical for boosting performance in cold climates. The new heat pumps might be half as expensive to operate as heating technologies now used in cold regions where natural gas is unavailable and residents rely on electric heaters and liquid propane.

“We’ll be able to extend the geographical range where heat pumps can apply,” said W. Travis Horton, an assistant professor of civil engineering. “So this could open up a whole new market.”

The vapor-compression cycle of standard heat pumps has four stages: refrigerant is compressed as a vapor, condenses into a liquid, expands to a mixture of liquid and vapor, and then evaporates. The new technology works by modifying the conventional vapor-compression cycle behind standard air conditioning and refrigeration.

“This could be a relatively simple modification to existing heat pumps, refrigeration and air conditioning systems,” said James Braun, a professor of mechanical engineering.